Lesson 78 provided students with additional practice converting from mass to moles and from moles to mass. The Lesson 78 PowerPoint ChemCatalyst activity asked students to predict whether arsenic (As), arsenic oxide (As2O3), or arsenic sulfide (As2S3) was most toxic. Students had to consider how many atoms of arsenic are in each molecule, and which has more molecules in a fixed mass. Some of the work from the entry task is shown below:

For the Lesson 78 Worksheet, students worked in pairs to complete the questions. For homework, students were assigned questions 5-8 from the textbook.